1st files gone, now the drive - cleared Dragon Branch & ran sfc

Hi,
The backstory is... I clicked on a close pop-up X on B&H Photo's website and Chrome was quickly covered in ads. I had Kaspersky Internet Security 2015 on my pc but it didn't detect anything before then. I tried system restore to the day before but it didn't solve the issue. After upgrading to KIS 2016 it found Dragon Branch and treated it. After a reboot it was back.

So I went into safe mode, disconnected from the internet and uninstalled it (it looked like it was installed with another program back in April), reset my browsers to their defaults, deleted temp internet files and emptied the recycling bin. I thought it was gone for a while, but then I noticed that files were missing from at least one of my internal hard drives. The files would be gone in a folder, but sub-folders remained (but were empty). For other files, I could see them but they won't open. While others were unaffected.

I saw on one of the forum pages to rebuild the search index. I started that but after 12 hrs, it was still less than 1/3 the way through (I have a lot of photo files). So I paused that and ran Malwarebytes - it found DragonBranch.A, OpenCandy and AceWebExtension.A. It treated them and after a reboot, rerunning Malwarebytes didn't find anything.

I then ran sfc /scannow - it found corrupt files but couldn't repair them all. So I ran it two more times (the post suggested that it may take 3 or more runs). At this point, I went to see if the files were back, but the hard drive itself wasn't showing up anymore.

Any ideas on what's happening? The CBS logs are attached.
Thank you

Hi all,
Looks like they were two separate events happening at the same time. I starting going down that line of thought thinking the hard drive simply failed. But on some reboots I get an error message that no keyboard is found, even with a usb keyboard. I read in a different post that that is a sign that the motherboard is failing. When I plug the usb keyboard into a usb slot on a pci card, there is no error.
I had tried reboots before and it made no difference with the current issue. Then, when I thought I was taking out the defective drive just now, I took out the boot drive instead. A reboot quickly pointed that out. When I put it back in, the missing drive was back!
So, I'm now thinking its a motherboard issue. I'm copying the files across to another drive, as I type, in case it is the drive and I got a lucky window of access. Its probably time to build a new PC.
Thanks